In an LTE-A system, with the decrease of a coverage area of cells and the trend that the frequency reuse factor approaches to 1, inter-cell interference has become a key problem which restricts the capacity of a cell. In order to improve spectral efficiency, a coordinated multi-cell transmission technique, also referred to as a Coordinated Multi-Point (CoMP) transmission technique, is proposed.
A basic idea of the coordinated multi-cell transmission is to associate multiple cells to transmit signals and share channel and data information of users in the associated cells through a wire channel such as fiber. The objective is to make the cells orthogonal to each other, so as to overcome the inter-cell interference and increase system throughput.
In the present invention, for facilitating the description, a set of multiple cells connected by the wire channel such as fiber is referred to as a super-cell. Generally, a super-cell is equipped with a central controller which has a core control function and is used for coordinating a coordinated transmission of the multiple cells. Except for the central controller, base stations of other cells may be configured as Remote Radio Equipment (RRE) without the core control function. It should be understood that, in order to overcome the inter-cell interference and increase throughput of the super-cell, all the cells in the super-cell may participate in the coordinated transmission at the same time. However, by this way, all the cells in the super-cell need to share a large amount of channel and user data information. As a result, the coordinated operation is rather complicated, while a coordinated gain obtained may be not high enough.
In order to solve the above problem of high complexity of the coordinated operation, the cells in the super-cell may be divided into at least one cooperating set which respectively participates in the coordinated transmission. In the existing LTE-A system, at least one cooperating set may be defined in advance in the super-cell. However, channel conditions of different users in the super-cell are different and channel information of a same user is also time-varying. Therefore, the manner of defining the cooperating set in advance lacks flexibility and cannot obtain a high coordinated gain. Besides, each user may select at least one cell according to its channel condition to form a cooperating set. However, in this manner, since different users may select different cooperating sets, the number of the cooperating sets may be rather large, which directly results in high complexity for scheduling of the cooperating sets. Therefore, a problem to be solved by the coordinated multi-cell transmission technique is how to dynamically determine cells and users participating in the coordinated transmission in the super-cell by considering both the performance of the coordinated transmission and the impact of the complexity.